Drop support for GHC 8.6 and GHC 8.8 (#314)

* Drop support for GHC 8.6 and GHC 8.8

* Update changelog

* Minor cleanup

.github/workflows/ci.yml

@@ -13,7 +13,7 @@ jobs:
       fail-fast: false
       matrix:
         os: [ubuntu-latest]
-        ghc: ['9.8.2', '9.6.3', '9.4.7', '9.2.8', '9.0.2', '8.10.7', '8.8.4', '8.6.5']
+        ghc: ['9.8.2', '9.6.3', '9.4.7', '9.2.8', '9.0.2', '8.10.7']
         include:
         - os: windows-latest
         # Testing on MacOS is disabled until GitHub actions support 'allow-failure'

CHANGES.md

@@ -2,8 +2,8 @@
 
 ## 0.8
 
-* #305: Support GHC 9.4 and GHC 9.6.
-* #303: Stop supporting GHC 8.4.
+* #305, #312: Support GHC 9.4, GHC 9.6 and GHC 9.8.
+* #303, #314: Stop supporting GHC 8.4, GHC 8.6 and GHC 8.8.
 
 ## 0.7
 

algebraic-graphs.cabal

@@ -12,7 +12,7 @@ homepage:      https://github.com/snowleopard/alga
 bug-reports:   https://github.com/snowleopard/alga/issues
 category:      Algebra, Algorithms, Data Structures, Graphs
 build-type:    Simple
-tested-with:   GHC==9.8.2, GHC==9.6.3, GHC==9.4.7, GHC==9.2.8, GHC==9.0.2, GHC==8.10.7, GHC==8.8.4, GHC==8.6.5
+tested-with:   GHC==9.8.2, GHC==9.6.3, GHC==9.4.7, GHC==9.2.8, GHC==9.0.2, GHC==8.10.7
 description:
     <https://github.com/snowleopard/alga Alga> is a library for algebraic construction and
     manipulation of graphs in Haskell. See <https://github.com/snowleopard/alga-paper this paper>

src/Algebra/Graph/Export.hs

@@ -37,7 +37,7 @@ import Algebra.Graph.Internal
 -- implementation uses difference lists). Here @s@ is the type of abstract
 -- symbols or strings (text or binary). 'Doc' @s@ is a 'Monoid', therefore
 -- 'mempty' corresponds to the /empty document/ and two documents can be
--- concatenated with 'mappend' (or operator 'Data.Monoid.<>'). Documents
+-- concatenated with 'mappend' (or operator 'Data.Semigroup.<>'). Documents
 -- comprising a single symbol or string can be constructed using the function
 -- 'literal'. Alternatively, you can construct documents as string literals,
 -- e.g. simply as @"alga"@, by using the @OverloadedStrings@ GHC extension. To
@@ -91,7 +91,7 @@ isEmpty (Doc xs) = null xs
 -- constructed directly from string literals (see the second example below).
 --
 -- @
--- literal "Hello, " 'Data.Monoid.<>' literal "World!" == literal "Hello, World!"
+-- literal "Hello, " 'Data.Semigroup.<>' literal "World!" == literal "Hello, World!"
 -- literal "I am just a string literal"  == "I am just a string literal"
 -- 'render' . literal                      == 'id'
 -- @
@@ -101,8 +101,8 @@ literal = Doc . pure
 -- | Render the document as a single string. An inverse of the function 'literal'.
 --
 -- @
--- render ('literal' "al" 'Data.Monoid.<>' 'literal' "ga") :: ('IsString' s, 'Monoid' s) => s
--- render ('literal' "al" 'Data.Monoid.<>' 'literal' "ga") == "alga"
+-- render ('literal' "al" 'Data.Semigroup.<>' 'literal' "ga") :: ('IsString' s, 'Monoid' s) => s
+-- render ('literal' "al" 'Data.Semigroup.<>' 'literal' "ga") == "alga"
 -- render 'mempty'                         == 'mempty'
 -- render . 'literal'                      == 'id'
 -- @

src/Algebra/Graph/Label.hs

@@ -71,7 +71,7 @@ Instances of this type class must satisfy the following semiring laws:
         > x <.> (y <+> z) == x <.> y <+> x <.> z
         > (x <+> y) <.> z == x <.> z <+> y <.> z
 -}
-class (Monoid a, Semigroup a) => Semiring a where
+class Monoid a => Semiring a where
     one   :: a
     (<.>) :: a -> a -> a
 

test/Algebra/Graph/Test/Arbitrary.hs

@@ -1,4 +1,3 @@
-{-# LANGUAGE CPP #-}
 {-# OPTIONS_GHC -fno-warn-orphans #-}
 -----------------------------------------------------------------------------
 -- |